Integrated circuits with aligned (100) NMOS and (110) PMOS finFET sidewall channels

ABSTRACT

An integrated circuit device that includes a plurality of multiple gate FinFETs (MuGFETs) is disclosed. Fins of different crystal orientations for PMOS and NMOS MuGFETs are formed through amorphization and crystal regrowth on a direct silicon bonded (DSB) hybrid orientation technology (HOT) substrate. PMOS MuGFET fins are formed with channels defined by fin sidewall surfaces having (110) crystal orientations. NMOS MuGFET fins are formed with channels defined by fin sidewall surfaces having (100) crystal orienations in a Manhattan layout with the sidewall channels of the different PMOS and NMOS MuGFETs aligned at 0° or 90° rotations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/855,520filed Apr. 2, 2013, which is a continuation of application Ser. No.13/425,082, filed Mar. 20, 2012 (now Pat. No. 8,410,519), which is acontinuation of application Ser. No. 13/036,938, filed Feb. 28, 2011(now Pat. No. 8,138,035), which is a continuation of application Ser.No. 11/764,442, filed Jun. 18, 2007 (now Pat. No. 7,897,994), theentireties of all which are hereby incorporated by reference.

BACKGROUND

This relates to methods of fabricating semiconductor devices with fieldeffect transistors having gates that straddle fins of channel formingmaterial (so-called FinFETs).

Conventional integrated circuit devices, such as SRAM devices, have NMOSand PMOS fin field effect transistors (FinFETs) with different channelcrystal orientations laid out in a non-aligned fin layout (referred toas a “non-Manhattan” layout). Adjacent fins of different conductivitytype are rotated by 45° to accommodate for the different crystalorientations of the substrate surfaces.

FIG. 1 (Prior Art) illustrates a conventional layout for a multiple gateFinFET (MuGFET) device 100. As shown, MuGFET 100 has a semiconductormaterial fin 130 straddled by a saddle-like gate 120. The fin 110 andgate 120 are formed on an oxide layer 140 (e.g., SiO₂) formed on asemiconductor substrate. The channels for MuGFET 100 are located on thesidewalls 150 of the fin 130. For a usual <110> notch (001) surfacewafer, the sidewall 150 of the fin 130 has a (110) crystal orientationif fin 130 is laid out at 0° or 90° rotation with respect to the notch.If the rotation of the fin 130 is laid out at 45° with respect to thenotch, the fin 130 sidewalls 150 will have a (100) crystal orientation.

A (110) crystal orientation surface is good for channel hole mobilitybut poor for channel electron mobility, while the (100) crystalorientation channel surface is poor for channel hole mobility but goodfor channel electron mobility. Thus, a (110) sidewall orientation is apreferred orientation for PMOS MuGFETs and a (100) sidewall orientationis a preferred orientation for NMOS MuGFETs. To provide preferredsurface orientations for PMOS and NMOS MuGFETs on the same substrate,conventional fabrication methods use mixed rotations of the fins 130 of0° (or 90°)and 45°. Such mixed rotations require increases in layoutarea of an integrated circuit device by approximately 25% and increaselithography difficulties.

FIG. 2A (Prior Art) illustrates a top view of an example non-Manhattanlayout design of a conventional SRAM storage cell which uses both PMOSand NMOS FinFETs. As shown, SRAM storage cell 200 has a plurality offins 210 with runs of 0° and 45° rotations straddled by gates 220. Fins210 have enlarged pad portions away from the gates 220 which providelocations for connection to source/drain regions by contacts 215. Gates220 have enlarged pad portions away from the fins 210 for connection togate electrodes by contacts 225. Using industry standards for spacingbetween components and measurements taken between centers of outsidecontact points of contacts 215, 225, the example conventional layout forSRAM storage cell 200 shown in FIG. 2 occupies a layout area ofapproximately 500 nm by approximately 812.5 nm, or approximately 406,250nm². (Elements of the layout for storage cell 200 given in FIG. 2A aremarked to show correspondence with source/drains S, D or S/D and gates Gof pull-up transistors PT1, PT2, drive transistors DT1, DT2 and accesstransistors AT1, AT2 of a typical storage cell schematic diagram such asgiven in FIG. 1 b of U.S. Pat. No. 7,087,493 which is reproduced as FIG.2B herein.)

SUMMARY

Embodiments described herein relate to methods for forming integratedcircuit devices having fin field effect transistors (FinFETs) withdifferent channel surface crystal orientations arranged in parallel orperpendicular alignment.

In a described example, an integrated circuit in the form of an exampleSRAM storage cell implementation has a first fin with a (110) crystalorientation sidewall defining a transistor channel of a PMOS FinFET inparallel alignment with a transistor channel of an NMOS FinFET definedby a second fin having a (100) crystal orientation sidewall.

The described methods enable PMOS FinFETs and NMOS FinFETs to be laidout in Manhattan layouts, i.e., fins rotated with respect to notches at0° and 90° . By avoiding 45° rotations, substrate area requirements formixed NMOS and PMOS FinFET layouts can be minimized. Moreover, enablinguse of Manhattan layouts having 0° and 90° rotations simplifiesphotolithography processes used for fabrication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (Prior Art) is a perspective view of a conventional fin fieldeffect transistor (FinFET) device.

FIG. 2A (Prior Art) is a top view of an example conventionalnon-Manhattan layout of an SRAM storage cell utilizing FinFETs of thetype shown in FIG. 1 having different channel surface crystalorientations.

FIG. 2B (Prior Art) is a schematic diagram of a conventional SRAMstorage cell as given in FIG. 1 b of U.S. Pat. No. 7,087,493.

FIGS. 3-6 illustrate steps in an example method of forming an integratedcircuit device having FinFETs with different channel surface crystalorientations in accordance with principles of the invention.

FIG. 7 is a top view of an example Manhattan layout of an example SRAMstorage cell utilizing FinFETs formed in accordance with the principlesof the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments of the invention are described for illustrativepurposes, with reference to FIGS. 3-6, in a context of a method offorming an integrated circuit device having PMOS and NMOS multiple gateFinFETs (MuGFETs) with aligned fins of different channel surface crystalorientations.

FIG. 3 shows a step of providing a direct silicon bonded (DSB) substrate300 having an upper silicon layer 310 with a (110) crystal orientationtop surface over a lower silicon substrate 320 with a (100) crystalorientation top surface. The upper silicon layer 310 includes the (110)top surface by virtue of its crystalline structure and the lower siliconsubstrate 320 includes the (100) top surface by virtue of itscrystalline structure. The DSB substrate 300 may be created usingconventional techniques for creating a DSB substrate 300.

FIG. 4 shows a later step wherein the DSB substrate 300 of FIG. 3 hasbeen processed using conventional photomask/hard mask and etchingpatterning techniques followed by an amorphorization implant toselectively amorphize a PMOS region 430 of the crystalline structure ofupper silicon layer 310. The crystalline structures of the lower siliconsubstrate 320 and remaining portions of the upper silicon layer 310outside the PMOS region 430 are not implanted during the PMOS regionamorphorization implant, so remain the same.

FIG. 5 shows a later step wherein the DSB substrate 300 of FIG. 4 hasbeen further processed to regrow and recrystallize the amorphizedsilicon within the amorphorized PMOS region 430 of upper silicon layer310. The amorphized silicon is regrown using the underlying crystallinestructure of the lower silicon substrate 320 as a template, therebygiving the recrystallized PMOS region 430 a (100) crystal orientationtop surface. The crystalline structures of the lower silicon substrate320 and the remaining portions of the upper silicon layer 310 outsidethe PMOS region 430 are not regrown and recrystallized during theregrowth and recrystallization of the amorphorized PMOS region 430, soremain the same.

FIG. 6 shows a later step wherein the DSB substrate 300 of FIG. 5 hasbeen further processed using conventional photomask/hard mask andetching patterning techniques to pattern the recrystallized PMOS region430 and unrecrystallized remaining portions of the upper silicon layer310 to form adjacent fins 630, 640 having sidewall surfaces of differentcrystal orientations laid out in general parallel planar alignment. Thepatterning removes parts of the recrystallized PMOS region 430 andremaining portions of the upper silicon layer 310 from around the fin630 to define a PMOS FinFET fin including a (110) crystal orientationsidewall channel and a (100) crystal orientation top surface. Thepatterning also removes parts of the remaining portions of the uppersilicon layer 310 from around the fin 640 to define an NMOS FinFET finincluding a (100) crystal orientation sidewall channel and a (110)crystal orientation top surface.

Thus, as described, using a hybrid orientation technology (HOT) directsilicon bonded (DSB) substrate 300 wherein the silicon DSB layer 310 hasa (110)-oriented crystal top surface and the silicon wafer substrate 320has a (100)-oriented top surface, PMOS FinFET regions in the DSB layer310 may be amorphized and regrown to form PMOS multiple gate FinFETs(MuGFETs) having (100)-oriented top surfaces and (110)-orientedsidewalls providing sidewall channels with hole mobility in the <110>direction in general parallel or perpendicular (0° or 90°) alignmentwith channels for electron mobility in the <100> direction provided byNMOS MuGFETs formed in unamorphized regions having (110)-oriented topsurfaces and (100)-oriented sidewalls.

FIG. 7 illustrates a top view of an example Manhattan layout design ofan SRAM storage cell 700 having a plurality of fins 710 straddled bygates 720. Fins 710 have enlarged pad portions away from the gates 720which provide locations for connection to source/drain regions bycontacts 715. Gates 720 have enlarged pad portions away from the fins710 for connection to gate electrodes by contacts 725. As for the layoutof fins 210 of SRAM storage cell 200 shown in FIG. 2, fins 710preferably have different sidewall crystal orientations for defining thechannels of PMOS FinFETs and NMOS FinFETs. However, in contrast to thefins 210 of SRAM storage cell 200, the layout of SRAM storage cell 700may be accomplished without the necessity for rotating the differentcrystal orientation sidewall fins 710 at 45° relative to each other. Inthe SRAM storage cell 700, the fins 710 can be laid out with fins 710 ofdifferent sidewall crystal orientations in 0° or 90° alignment. Fins 710for PMOS FinFETs may be formed as described above for patterned fins 630and fins 710 for NMOS FinFETs may be formed as described above forpatterned fins 640.

Using industry standards for spacing between components and measurementstaken between centers of outside contact points of contacts 715, 725,the example layout for SRAM storage cell 700 shown in FIG. 7 occupies alayout area of approximately 475 nm by approximately 755 nm, orapproximately 358,625 nm². This provides a 47,625 nm² (or approximately25% reduction) in area over the 406,250 nm² area of the conventionallayout shown in FIG. 2. (As for the layout for the storage cell 200given in FIG. 2, elements of the layout for storage cell 700 given inFIG. 7 are marked to show correspondence with source/drains S, D or S/Dand gates G of pull-up transistors PT1, PT2, drive transistors DT1, DT2and access transistors AT1, AT2 of the storage cell schematic diagram ofFIG. 2B.)

The principles disclosed herein apply equally to forming fins of NMOSFinFETs with (110)-oriented sidewall surfaces (<110> channel direction)and (100)-oriented top surfaces and to forming fins of PMOS FinFETs with(100)-oriented sidewall surfaces (<100> channel direction) and(110)-oriented top surfaces on a common substrate having the(110)-oriented top surface DSB layer at 0° and 90°. Incorporating a PMOSFinFET having a (100)-oriented sidewall surface on a common substratewith an NMOS FinFET also having a (100) crystal orientation sidewallsurface might be done, for example, when it is considered advantageousto have a weak PMOS transistor and a strong NMOS transistor for an SRAMwrite operation.

The same principles may also be applied to a hybrid orientationtechnology (HOT) direct silicon bonded (DSB) substrate 300 having a(100)-oriented top surface upper layer over a (110)-oriented top surfacewafer substrate. In such case, a region of the upper layer is amorphizedand regrown to have a (110)-oriented top surface crystal orientation,with unamorphized portions left with the original (100)-oriented topsurface.

The same principles may also be applied to a DSB substrate having same(100)-oriented top surfaces on both the upper silicon layer and thelower silicon substrate. In such case, the DSB top layer's notch isrotated by 45° relative to the DSB substrate, placing the NMOS FinFETchannel direction in a <100> direction instead of a <110> direction,prior to further processing as disclosed above.

Moreover, the principles disclosed herein also make a (111)-orientedsurface accessible by aligning a fin layout to a <112> direction on a(110)-oriented substrate surface. All three primary crystal surfaces areaccessible to semiconductor devices using the principles disclosedherein.

Although the example disclosed herein is applied to a DSB substrate, theteachings disclosed herein may also be applied to other hybridorientation substrates having a (110) crystal orientation on surfacelayer and a (100) crystal orientation surface layer.

Those skilled in the art to which the invention relates will appreciatethat modifications to the above embodiments and additional embodimentsare possible within the scope of the claimed invention.

What is claimed is:
 1. An integrated circuit device, comprising: a lower silicon layer having a top surface with a first crystal orientation; an upper silicon layer on the lower silicon layer having a first portion with a top surface of a second crystal orientation different from the first crystal orientation and a second portion with the top surface of the first crystal orientation; a first fin in the second portion of the upper substrate, the first fin having a top surface with a first crystal orientation and a sidewall surface with a second crystal orientation; and a second fin in the first portion of the upper substrate, the second fin having a top surface with the second crystal orientation and a sidewall surface with the first crystal orientation; the first fin sidewall surface defining a channel with a first carrier flow direction of a first FinFET, the second fin sidewall defining a channel with a second carrier flow direction of a second FinFET, and the second carrier flow direction being different than the first carrier flow direction.
 2. The integrated circuit device of claim 1, wherein the first crystal orientation is (100) and the second crystal orientation is (110). 